Adult mongrel dogs were subjected to creation of ipsilateral carotid-jugular and femoral-femoral arteriovenous fistulas as well as corresponding arteriotomies on the contralateral side. Animals were then sacrificed at 24, 48, and 72 hours as well as at 4 weeks to one year following shunting. All were given an intravenous dose of Evan's Blue Dye, U.S.P., 1.5 cc/Kg, 24 hours prior to sacrifice. At sacrifice, vessels were harvested on both shunted and nonshunted sides and scanned with a photosensitive cell capable of detecting Evan's Blue Dye concentration. Microscopic sections of vessels were also taken.